Now, Pennsylvania State University researchers have identified two odd traits that also seem to help:
One is the distance between the Achilles tendon and the center of the ankle joint. The other: the length of your toes.
When the scientists measured 24 people, half sprinters and half not, the speedy folks had big toes that were 9 millimeters longer, on average (8.2 cm vs. 7.3 cm for regular people.) The sprinters' Achilles measurements were also 25 percent smaller.
Both findings initially surprised Stephen J. Piazza, an associate professor of kinesiology. He and graduate student Sabrina Lee followed up with computer models.
Long toes allow a sprinter to stay in contact with the ground longer for those first steps that require a powerful pushoff, the model showed.
"The only way you can accelerate your body is through interaction with the ground," Piazza says, adding that long toes could be a disadvantage for distance runners.
Less intuitive is the Achilles measurement, but Piazza likens it to the handles on a wheelbarrow. Long handles make it easier to lift a load, but that also means you have to lift farther (just like being farther out on a seesaw.)
In the ankle, that Achilles distance is akin to the length of the handles, with the ball of the foot as the "wheel," Piazza says.
In order to push the body off the ground, the calf muscles must contract. People with shorter Achilles "handles" don't shorten the calf muscles as fast - enabling them to generate more force, Piazza says.
The shorter handles give them somewhat less leverage, but that is outweighed by the muscular advantage, he says.
Could a measuring tape be the track coach's new tool?
- Tom Avril
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